new-payload-with-witness + BAL/witness prerequisites (historical accesses) in snapshots

[yperbasis]

• Prototype Introduction of REST based + SSZ serialized new-payload-with-witness ethereum/execution-apis#773 or engine: add Rest-SSZ spec ethereum/execution-apis#793 (comment).
• Store a superset of BALs and witnesses so that we don't have to re-execute to get BALs or witnesses. Then we can produce BALs and witnesses on the fly, so we don't need to store them in the DB.

[VBulikov]

yperbasis added Imp1 as Importance